Water Rocket Forum

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A water rocket is a type of model rocket using water as its reaction mass. The pressure vessel (the engine of the rocket) is constructed from thin plastic or other non metallic materials (usually a used plastic soft drink bottle) weighing 1,500 grams or less. The water is forced out by compressed air. It is an example of Newton's third law of motion.

Clarification question on rules (particularly class D, which the current record, by my own physics-based simulations, is right near the theoretical limit for a 2L bottle, so it won't get beaten by much if at all):

Are 3-D printed parts allowable? There are several nuances to this question. Consider these four scenarios:

I design my own part, and create it in virtual space in my computer, and then send the file to my own 3-D printer.

I use a friend's 3-D printer to print the virtual part I created myself.

I create the part myself and then send the saved file to one of the many available commercial 3-D printing services for them to print and send me back my part.

I download a design I find online and 3-D print it myself on my own 3-D printer.

My own take on this, is that I must be the person who creates and builds the part in a virtual 3-D space. The final step of printing out a part has nothing to do with my skill in creating it (you just load the file into the printer and push a button), so it doesn't matter who prints it for me. Therefore I'd consider scenarios 1, 2, and 3 to be allowable.

On the other hand, if I print someone else's model of a part, I'm not actually doing any creative work, I didn't design the part, and I didn't create it in a virtual 3D space, someone else did. So even if I used my own printer, I would say scenario 4 isn't allowable.

You are correct that options 1 - 3 would be acceptable. For #4 it would depend on a few things. A "downloaded" 3d model that you did not design may or may not be acceptable. A 3d model you purchase would not but a "free" model may. I would recommend if you are in that situation to ask before you build and we will handle it on a case by case basis until we can gather the membership and add a specific section detailing what will be allowed with 3d printing.

Lisa Walker,Forum Administrator. The Water Rocket Achievement World Record Association